As is well known, liquid fuels such as oil and gasoline are becoming scarce and expensive, while solid fuels such as coal, pulverized vegetation, and the like remain abundant but more difficult to use in internal combustion engines. That is, solid fuels have heretofore been both difficult to accurately meter and feed, while likely to cause substantial wear on the engine parts. Further, the prior art has not provided a simple, but highly effective means for feeding solid fuel in an engine which can be converted to the use of semi-solid, liquid and solid fuels.